adjective

(of evidence or argument) having or likely to have the effect of proving a case; decisive.

conclusive evidence

incontrovertible,incontestable,irrefutable,unquestionable,undeniable,indisputable,unassailable,beyond dispute,beyond question,beyond doubt,beyond a shadow of a doubt,certain,decisive,convincing,clinching,definitive,definite,positive,final,ultimate,categorical,demonstrative,unequivocal,unarguable,unanswerable,uncontroversial,airtight,watertight